html5 拖拽及用 js 实现拖拽

时间:2020-10-22 15:52:00 来源:互联网 作者: 神秘的大神 字体:

1. HTML5 拖拽

1.1 相关知识

拖拽元素:可以为元素添加 draggable="true"来让元素能够被拖拽。

拖拽元素的事件监听:(应用于拖拽元素)

  • ondragstart拖拽开始时调用
  • ondragleave鼠标离开拖拽元素时调用
  • ondragend拖拽结束时调用
  • ondrag 整个拖拽过程都会调用

目标元素:把元素A拖拽到元素B里,那么元素B就是目标元素。页面中任何一个元素都可以成为目标元素。

目标元素的事件监听:(应用于目标元素)

  • ondragenter 当拖拽元素进入时调用
  • ondragover 当拖拽元素停留在目标元素上时,就会连续一直触发(不管拖拽元素此时是移动还是不动的状态)
  • ondrop 当在目标元素上松开鼠标时调用
  • ondragleave 当鼠标离开目标元素时调用

如果想让拖拽元素在目标元素里做点事情,就必须要在 ondragover() 里加event.preventDefault()这一行代码。

1.2 拖拽基础

代码

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
        <style>
            .box {
                width: 200px;
                height: 200px;
                background: green;
            }
            .box2 {
                position: relative;
                left: 300px;
                top: 50px;
                width: 300px;
                height: 300px;
                background: red;
            }
        </style>
    </head>
    <body>
        <div class="box" draggable="true"></div>
        <div class="box2"></div>
        <script>
            // HTML5 拖拽
            // 应用于拖拽元素
            var box = document.querySelector('.box')
            box.ondragstart = function () {
                console.log('拖拽开始')
            }
            box.ondragleave = function () {
                console.log('鼠标离开元素')
            }
            box.ondragend = function () {
                console.log('拖拽结束')
            }
            // box.ondrag = function () {
            //     console.log('在拖拽');
            // }

            // 应用于目标元素(想把 box 拖拽进去的地方)
            var box2 = document.querySelector('.box2')
            box2.ondragenter = function () {
                console.log('进来了')
            }
            box2.ondragleave = function () {
                console.log('离开了')
            }

            // 当拖拽元素在 目标元素上时,连续触发
            box2.ondragover = function (e) {
                // 如果想让拖拽元素在目标元素里做点事情,就必须要在 ondragover() 里加event.preventDefault()这一行代码。
                e.preventDefault()
                console.log('over')
            }
            box2.ondrop = function () {
                console.log('松开鼠标了')
            }
        </script>
    </body>
</html>

1.3 将 A 在 B、C 之间拖拽

代码

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
        <style>
            .box-b {
                width: 250px;
                height: 250px;
                background: green;
            }
            .cell-a {
                float: left;
                width: 50px;
                height: 50px;
                margin: 5px;
                text-align: center;
                line-height: 50px;
                border-radius: 50%;
                background: red;
            }
            .box-c {
                width: 200px;
                height: 200px;
                margin-top: 10px;
                background: skyblue;
            }
        </style>
    </head>
    <body>
        <p>boxB</p>
        <div class="box-b">
            <div class="cell-a" draggable="true">1</div>
            <div class="cell-a" draggable="true">2</div>
            <div class="cell-a" draggable="true">3</div>
            <div class="cell-a" draggable="true">4</div>
            <div class="cell-a" draggable="true">5</div>
        </div>
        <p>boxC</p>
        <div class="box-c"></div>
        <script>
            var cellA = document.querySelectorAll('.cell-a')
            var boxB = document.querySelector('.box-b')
            var boxC = document.querySelector('.box-c')
            var temp = null

            cellA.forEach((cell, index) => {
                // 从 boxB 拖拽到 boxC
                cell.ondragstart = function () {
                    // 保持当前拖拽的元素
                    temp = this
                }
                cell.ondragend = function () {
                    temp = null
                }
                boxC.ondragover = function (e) {
                    e.preventDefault()
                }
                boxC.ondragenter = function () {
                    this.appendChild(temp)
                }

                // 从 boxC 拖拽到 boxB
                boxB.ondragover = function (e) {
                    e.preventDefault()
                }
                boxB.ondragenter = function () {
                    this.appendChild(temp)
                }
            })
        </script>
    </body>
</html>

效果展示

2. 用 js 实现拖拽

2.1 js 简单拖拽

按下鼠标进行简单的拖拽。

代码

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
        <style>
            #box {
                position: absolute;
                width: 200px;
                height: 200px;
                background: green;
            }
        </style>
        <script>
            window.onload = function () {
                var box = document.getElementById('box')
                var disX = 0
                var disY = 0

                box.onmousedown = function (e) {
                    var e = e || window.event
                    disX = e.clientX - this.offsetLeft
                    disY = e.clientY - this.offsetTop
                    box.onmousemove = function (e) {
                        var e = e || window.event
                        box.style.left = e.clientX - disX + 'px'
                        box.style.top = e.clientY - disY + 'px'
                    }
                    box.onmouseup = function (e) {
                        console.log('end')
                        this.onmousemove = null
                    }
                    return false
                }
            }
        </script>
    </head>
    <body>
        <div id="box"></div>
    </body>
</html>

效果展示

2.2 带效果的拖拽

代码

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Document</title>
        <style>
            .box {
                position: absolute;
                width: 200px;
                height: 200px;
                background: skyblue;
            }
            .box1 {
                position: absolute;
                border: 1px dashed black;
                opacity: 0.5;
            }
            .way-box {
                position: absolute;
                bottom: 30px;
                right: 30px;
                /* 无法选中 */
                -moz-user-select: none; /* 火狐 */
                -webkit-user-select: none; /* 谷歌 */
                -ms-user-select: none; /* IE */
                user-select: none;
            }
        </style>
        <script>
            window.onload = function () {
                ;(function () {
                    var box = document.querySelector('.box')
                    var disX, disY, temp
                    var body = document.querySelector('body')
                    var way1 = document.querySelector('#way1')
                    var way2 = document.querySelector('#way2')

                    box.onmousedown = function (e) {
                        var e = e || window.event // 兼容性写法
                        disX = e.clientX - this.offsetLeft
                        disY = e.clientY - this.offsetTop

                        temp = document.createElement('div')
                        body.appendChild(temp)
                        temp.classList.add('box')
                        temp.classList.add('box1')
                        // 移动后位置会变,temp 的位置应该与 box 位置重合
                        temp.style.left = e.clientX - disX + 'px' // 记得加单位!
                        temp.style.top = e.clientY - disY + 'px'

                        temp.onmousemove = function (e) {
                            var e = e || window.event
                            temp.style.left = e.clientX - disX + 'px' // 记得加单位!
                            temp.style.top = e.clientY - disY + 'px'
                        }
                        temp.onmouseup = function (e) {
                            console.log('end')
                            this.onmousemove = null
                            // 1 则默认不发生实际移动
                            if (way2.checked) {
                                box.style.left = e.clientX - disX + 'px'
                                box.style.top = e.clientY - disY + 'px'
                            }
                            temp.style.display = 'none'
                            this.onmouseup = null
                        }
                    }
                })()
            }
        </script>
    </head>
    <body>
        <div class="box"></div>
        <div class="way-box">
            <p>请选择拖拽的方式</p>
            <input type="radio" id="way1" name="way" checked />
            <label for="way1">1</label>
            <input type="radio" id="way2" name="way" />
            <label for="way2">2</label>
        </div>
    </body>
</html>

效果展示

有时会卡顿,未解决…